Thermal Behavior of Graded Ta‐Si/Ta‐Si‐N Diffusion Barriers for Cu Metallization

Using glancing angle X‐ray diffraction, glow discharge optical emission spectroscopy, and transmission electron microscopy, the crystallization behavior and thermal stability of graded Ta‐Si/Ta‐Si‐N diffusion barriers was analyzed after annealing at various temperatures. For a Ta30Si18N52/Ta73Si27 bilayer and a Ta73Si27/Ta30Si18N52/Ta73Si27 trilayer, nitrogen redistribution within the whole barrier is observed at Tan ⩾ 500 °C. Further heat supply leads to barrier crystallization into Ta2N. Depositing the layer stacks directly onto silicon, a critical temperature of Cu silicide formation was determined. For graded Ta‐Si/Ta‐Si‐N diffusion barriers, this temperature turned out to be between the corresponding values for Ta73Si27 and Ta30Si18N52 single layers.